SF 

^ I Issued May SI, 1910. 

J](,^ U. S. DEPARTMENT OF AGRICULTURE, 



BUREAU OF ANIMAL INDUSTRY.— BULLETIN 123. 

A. D. MELVIN, Chief of Bureau. 



THE INFLUENCE OF LACTIC ACID ON THE QUALITY 
OF CHEESE OF THE CHEDDAR TYPE. 



BY 



If^ 



U.^ 



C: F. DOANE, 

Assistant Dairyman, Dairy Division. 





WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1910. 




Class 'gs F'^7 ( 

Book • II(o^, 



Issued May 31, 1910. 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ANIMAL INDUSTRY.— Bulletin 123. 

A. D. MELVIN, Chief of Bureau. 



THE INFLUENCE OF LACTIC ACID ON THE QUALITY 
OF CHEESE OF THE CHEDDAR TYPE. 



BY 



C. F. DOANE, 
Assistant Dairyman, Dairy Division. 




r 



WASHINGTON: 
GOVERNMENT PRINTING OFFICE. 

1910. 



K}.^y--^ 



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THE BUREAU OF ANIMAL INDUSTRY. 



Chkf: A. D. Melvin. 

Assistant Chief: A. M. Farrington. 

Chief Clerk: Charles C. Carroll. 

Animal Ilusbandry Division: George M. Rommel, chief. 

Biochemic Division: M. Dorset, chief. 

Dairy Division: B. H. Rawl, chief. 

Inspection Division: Rice P. Steddom, chief; Morris \Yooden, R. A. Ramsay, and 

Albert E. Behnke, associate chiefs. 
Pathological Division: John R. Mohler, chief. 
Quarantine Division: Richard W. Hickman, chief. 
Zoological Division: B. H. Ransom, chief. 
Experiment Station: E. C. Schroeder, superintendent. 
Editor: James M. Pickens. 

9 



JUfJ 1 lyio 



LETTER OE TRANSMITTAL. 



U. S. Department of Agriculture, 

Bureau of Animal Industry, 
Wasliington, D. C, March I4, 1910. 
Sir: I have the honor to transmit the accompanying manuscript 
of an article entitled "The Influence of Lactic Acid on the Quality 
of Cheese of the Cheddar Type/' by C. F. Doane, of the Dairy Divi- 
sion of this Bureau. Mr. Doane has for some time been stationed at 
one of the principal cheese-makmg centers of the country, carrying 
on work connected with the manufacture and storage of cheese under 
practical conditions. The experiments described in the present 
paper have resulted in establishing data which are contrary to the 
usual practice of factories producing the Cheddar type of cheese, and 
are therefore calculated to be of value to this section of the cheese- 
making industry. I recommend the publication of the article in the 
bulletin series of this Bureau. 
Very respectfully, 

A. D. Melvin, 
Chief of Bureau. 
Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS. 



Page. 

Introduction 5 

Lactic-acid problems in cheese making 5 

Effect of high acidity on quality of storage cheese 11 

Experimental work to test effect of acid on flavor 14 

Results of experiments contrary to general practice 16 

The use of starter in milk 18 

Effect of early storage on acid cheese .^ 18 

Conclusions 20 



ILLUSTRATIONS. 



Page. 
Fig. 1. Diagram showing relation of acidity to score of cheese at various periods 

and temperatures 14 

2. Diagram showing relation of acidity to score of high-acid and normal 

cheese 16 



THE INFLUENCE OF LACTIC ACID ON THE QUALITY 
OF CHEESE OF THE CHEDDAR TYPE. 



INTRODUCTION. 

The relation of lactic acid to the science of cheese making, par- 
ticularly its action under varying conditions, and the necessity, or 
otherwise, for its development during the process of manufacture, 
are among the greatest unsolved problems connected with the dairy 
industry. 

In the making of the Cheddar type of cheese at the present time 
the expert cheese maker is chiefly concerned with this development 
of lactic acid, and his entire ability is exerted to secure a uniformity 
of cooking with the development of the acid. This is desired because . 
it is believed that a maximum quantity of acid is necessary for the best 
results. This maximum development is determined by the amount 
of acid that the curd will stand in the whey at the time of drawing 
the latter without subsequent injury to the texture and the color of 
the cheese. The best cheese makers are agreed, almost without excep- 
tion, that on this development of acid depends to a great extent the 
delicate flavor that the best cheese should have, also, the desired 
closeness of body, as well as some of the qualities of texture found in 
the best cheese. Under the present conditions, therefore, there is 
ample opportunity for the exhibition of skill in handling the milk and 
the curd, since the attainment of even a small degree of success in 
securing uniformity of the different processes under varying conditions 
comes only with long practice and keen observation. 

LACTIC- ACID PROBLEMS IN CHEESE MAKING. 

There is undoubtedly much yet to be learned concerning the 
development of lactic acid and its effects in cheese making. One 
apparent inconsistency lies in the differing effects of the lactic acid 
which is developed before, as compared with that which is devel- 
oped after, the whey is drawn. It it well known that the develop- 
ment of acid in the whey beyond approximately 0.2 per cent will 

5 



6 INFLUENCE OF LACTIC ACID ON QUALITY OF CHEESE. 

result in an acid cheese, although a slight variation from this will 
depend upon whether the milk is working fast or slow. A high- acid 
condition has a decidedl}^ injurious effect on the texture and the 
color of the cheese, and the greater the development of acid in the 
whey beyond the above limit the more pronounced is the injury. On 
the other hand, after the whey is drawn and the curd is put on the 
rack, the acid may develop until the expressed whey shows a full 1 
per cent, or even more, without any injury to texture or color. This 
would certainly appear to be inconsistent. In both cases the acid 
formed is evidently lactic acid. In both cases the acid is formed 
inside of the curd particles, as the greater part of the bacteria are 
carried down into the curd after setting the milk and cutting the curd," 
and the acid is formed in the curd and expelled into the whey. We 
have, then, in each case a process of acid formation operating under 
such similar conditions as to be apparently identical, yet the results 
are radically different. While in the whey a development of 0.3 per 
cent of lactic acid will practically ruin the commercial value of the 
cheese, yet in the matted curd more than three times this quantity 
may develop with what most cheese makers believe to be a benefit, 
and certainly without apparent injury. 

In the best present-day practice in cheese making there is an 
attempt to develop all the acid possible without injury to the texture 
and color of the product. To begin with, a maximum amount of acid 
is developed in the whey, and finally the curd is allowed to remain on 
the rack until all the acid that will develop in a practicable length of 
time is obtained. But while there are many positive opinions in 
regard to the good results of this method, there is but little accurate 
knowledge. The effect of acid on flavor is not known, and, contrary 
to general opinion, a glance at some of the tables included in this 
paper will show that a flat or low flavor may be found in a high-acid 
cheese. Again, the actual effects of a so-called proper development 
of acid on the closeness or the texture of tlie cheese is not known. 
The desired characteristics of texture, body, and flavor may be found, 
and have been found on numberless occasions, when the curd has 
been worketl through comparatively sweet. 

However, we know bej'ond doubt that a high acid development in 
the whey will injure the resulting product. Furthermore, we have 
very good reason to believe that a high acid development in the curd 
made from so-called gassy milk is necessary to overcome the gas, and 
it may at the same time prevent a full development of the undesirable 
flavors attending gassy curds. 

« J. L. Sammis. Factors controlling the moisture content of cheese curds. U. S. 
Department of Agriculture, Bureau of Animal Industry, Bulletin 122. 



INFERIORITY OF HIGH-ACID CHEESE. 



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EFFECT OF HIGH ACIDITY. 11 

EFFECT OF HIGH ACIDITY ON QUALITY OF STORAGE CHEESE. 

The attention of the writer was called to one phase of this acid 
question at the time of scoring the cheese in the storage experiments 
made in the summer of 1906. A representative of the Dairy Division 
visited a number of cheese factories near Plj-mouth, Wis., that were 
having trouble with their product, and secured a quantity of cheese 
for storage. Most of these lots of cheese turned out to be high acid, 
and it was noted that where this was the case the qualit}^ was so very 
low as to make it appear that the acid was responsible in part at least 
for the poor flavor, as well as for the other undesirable characteristics 
always found in a high-acid cheese. 

The cheese in question was obtained for the purpose of determining 
the effect of storage on different kinds of poor cheese. It was pur- 
chased in July and August and was scored in January. The scores 
are given in Table 1 . Because of the large proportion of this cheese 
that turned out to be high acid the work as planned was not satis- 
factory, but it did show the tendency to make high-acid cheese when 
troubles with bad milk are experienced, and it illustrated very well 
the probable effect of high acid on the quality of the product. There 
were 34 lots of the cheese, each consisting of 8 cheeses, one-half of which 
were stored in the 32° F. room at various periods ranging up to two 
weeks, the other half being similarly placed in the 40° F. room. The 
average score on flavor for the high-acid cheese was 27, while the 
average on the normal acid cheese was 31. The comparatively poor 
flavor of ail the high-acid cheese was so marked that all who were 
connected with the scoring of this cheese noticed it and commented 
upon it. 

The Dairy Division made some high-acid cheese in the summer of 
1906 to determine the effects of storage on this quality of product. 
The cheese was made from exceptionally good milk, and the flavor 
should have been, in some of the lots at least, above criticism. Nine 
lots of cheese were made with varying amounts of acid. Quite a 
wide variation in the percentages of acid was sought, especially at 
the time the whej was drawn, as the degree of acidit}" at this period 
influences the quality of the cheese more than the acidity shown at 
any other period of its manufacture. The acid at the time of setting 
was regulated to suit the percentage desired at the time of drawing 
the whey. The percentages of acid at different stages of manufac- 
ture are shown in Table 3. 

Eight cheeses were made in each lot. These were stored two at a 
time — one at 32° F. and the other at 40° F. — at each of the following 
periods: Fresh from the press, four days old, one week old, and two 
weeks old. All the cheese was scored by three judges working inde- 
pendently, and Table 2 gives the average scores. Table 4, abstracted 



12 



INFLUE^'CE OF LACTIC ACID ON QUALITY OF CHEESE. 



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EFFECT OF HIGH ACIDITY, 



13 



from Table 2, and figure 1 are arranged to show more clearly the rela- 
tion of the numerical score to the acidity. Not all the scores are 
given, but those omitted are in line with those given. Enough are 
given to show conclusively the effect of the high acid on the cheese. 



Table 3. 



-Acidity at stated periods of high-acid cheese used in storage experiments and 
scored in Table 2. 



No. of 
lot. 


Acidity 
when 
set. 


Acidity 
when 
cut. 


Acidity 
when 
drawn. 


1 

2 

3 

4 

5 

6 

7 

8 

9 


Per cent. 
0.175 
.175 
.185 
.195 
.260 
.200 
.175 
.182 
.170 


Per cent. 
0.120 


Per cent. 
0.207 
.229 
.240 
.215 
.303 
.225 
.220 
.211- 
.220 






.184 
.145 


'.m 



Table 4. — Relation of the numerical score to the acidity of cheese described in Table 2. 



Num- 
ber 
of lot. 


Acid- 
ity. 


32° room, at once. 


32° room, one week. 


40° room, two weeks. 


Flavor. 


Tex- 
ture. 


Total. 


Flavor. 


Tex- 
ture. 


Total. 


Flavor. 


1^. Total. 


1 

8 
4 
7 
9 
6 
2 
3 
5 


Per ct. 

0.207 
.211 
.215 
.220 
.220 
.225 
.229 
.240 
.303 


311 

271 

25 

26§ 

26J 

28i 

23| 
20 


26J 

22J 

25 

24 

25i 

24J 

22J 

14 


82 

71S 

67 

72J 

71 

74i 

721 

67 

49i 


26§ 

27 

22§ 

25J 

25J 

26 

24^ 

23J. 


23§ 

24 

18 

23 

22 

24 

23* 

isl 


72i 
VIJ 
58i 

m 

66J 
70 
68J 
OIJ 


26§ 

241 

22 

20J 

24§ 

25 

26i 

21* 

18J 


25 

18J 

22J 

211 

21§ 

18J 

17 

14J 


75J 

67S 

58J 

681 

65 

C5J 

63§ 

56 

47§ 















It has already been stated that the above cheese was made as far 
as could be judged from perfect milk and that the curds worked through 
in excellent shape. At least a few cheeses should have been of excel- 
lent quality; but it appears that the quality was injured in about 
the same proportion as the amount of acid developed. The cheese 
in lot 1 was made with acid very slightly in excess of normal, and the 
cheese from this lot that was placed in the 32° room at once scored 82, 
while the similarly treated cheese in lot 5 was made with much too high 
a development of acid and scored a fraction less than 50. It is prob- 
able that cheese made from good milk would never score as low as 
50 points or as low as 20 points in flavor if it had been treated nor- 
mally in all stages of making and curing. Hence it would appear 
very probable that the high-acid development was responsible in part, 
at least, for the poor flavor. These results were so contrary to all 
belief and teaching; that it was thought desirable to make some 



14 



INFLUENCE OF LACTIC ACID ON QUALITY OF CHEESE. 



accurate comparative tests that would settle the question be3'ond 
controversy. For this purpose the author spent some time at a 
factor}^ near Plymouth, Wis., and carried out the experiments 
described in the followino; pages. 

EXPERIMENTAL WORK TO TEST EFFECT OF ACID ON FLAVOR. 

Sixteen lots of cheese were made for these experiments. Two lots 
were made each day from vats of divided milk so as to have identical 
conditions as regards quality of milk. One of these lots was worked 
up with just sufficient acid in the whey to make a light-acid cheese, 
the other lot being worked up on the same day in the regular way 
for that factory. The cheese maker in charge of this factory set his 



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Fig. 1.— Diagram showing relation of acidity to score of cheese at various periods and temperatures. 

milk and drew tlie whey somewhat sweeter than is customary among 
the best cheese makers; but the curd was allowed to develop the acid 
on the rack until all danger of gas had passed. Table 5 shows some of 
the details of the manufacture of each lot. 

The cheese was made during the first half of September, 1907, and 
each lot was held in the factory curing room one week before being 
placed in storage. The storage room was held at about 33° F. The 
cheese was scored in the middle of January, 1908, by J. W. Moore and 
Robert McAdam, of the Dairy Division, both experienced cheese 
makers and judges. The average score of each cheese is shown in 
Tal)le 6, and the relation of the numerical score to the acidity is 
graphicall}' shown in figure 2. 



EFFECT OF HIGH ACIDITY ON FLAVOR. 15 

Table 5. — Details of manufactvre of cheese for test of high acid oyi flavor. 



Lot. 


Time 
set. 


Acidity 
wtien 
set. 


Time 
cut. 


Time 
drawn. 


Acidity 
when 
drawn. 


Curd 
ground. 


Curd 
salted. 


Remarks. 




a. m. 


Per cent. 


a. m. 


a. m. 


Per cent. 


p. m. 


p. m. 






1, acid 


7.52 


0.17 


8.25 


11.00 


0.23 


1.15 


1.40 


Curd firm; few pin holes 
flavor. 


; bad 


1, sweet.. 


7.45 


.17 


8.25 


10.00 


.17 


12.30 


2.15 


Numerous pin holes; bad 
same as acid vat. 


flavor, 


2, acid.... 


8.30 


.20 


8.50 


9.55 


.20 


12.20 


1.30 


Oood curd. 




2, sweet. - 


7.20 


.17 


7.55 


9.15 


.15 


12.30 


1.30 


Do. 




3, acid.... 


8.10 


.20 


8.30 


9.55 


.20 


11.45 


12.30 


Good curd; slight taint. 




3, sweet.. 


7.40 


.175 


8.20 


9.45 


.16 


12.00 


12.30 


Few pin holes; slight taint. 




4, acid 


7.50 


.20 


8.20 


9.35 


.21 


12.05 


1.00 


Gassy. 




4, sweet.. 


7.40 


.17 


8.20 


9.45 


.18 


12.45 


1.30 


Do. 




5, acid 


10.00 


.20 


10.20 


11.55 


.21 


2.20 


3.30 


Slight taint; pin holes. 




5, sweet.. 


8.50 


.17 


8.45 


10.40 


.16 


1.00 


2.30 


Do. 




6, acid 


8.40 


.20 


9.02 


10.45 


.20 


1.00 


2.15 


Do. 




6, sweet.. 


8.00 


.19 


8.30 


10.30 


.16 


12.40 


2.00 


Do. 




7, acid 


8.52 


.20 


9.15 


10.45 


.20 


1.00 


2.00 


Shght taint. 




7, sweet.. 


8.10 


.18 


8.50 


ia.50 


.18 


2.00 


3.00 


Slight taint; few pin holes. 




8, acid.... 


9.20 


.145 


9.40 


11.30 


.19 


1.30 


2.30 


Slight taint; pin holes. 




8, sweet.. 


7.45 


.175 


8.32 


10.45 


.16 


1.15 


2.00 


Do. 





Table 6. — Average scores of cheese described in Table 5. 



Numerical score. 



Per ct. 
0.23 
.17 
.20 
.15 
.20 

.16 
.21 

.18 
.21 

.16 
.20 

.16 
.20 



.18 
.19 
.16 



Descriptive score. 



Flavor. 



Sour whey, sweet. . . 

Sweet 

Sour, bitter, unclean. 

Unclean 

Very unclean, sweet, 

sour whey. 

Trifle sweet 

Unclean, sweet 

Sweet 

Sour whey, bitter, 

sweet. 

Slightly sweet 

Sour whey, bitter, 

sweet. 

Sweet 

Fermented, sour 

whey, bitter, 

sweet. 

Tainted, sweet 

Sour, bitter, sweet.. . 



Coarse, mealy, stiff. 
Mechanical holes . . . 
Short, pasty, mealy. 
Mechanical holes. . . 
Crumbly, mealy 



Coarse 

Short, mealy 

Coarse " 

Crumbly, mealy, 
salvy. 

Uneven 

Mealy, soggy 



Uneven 

Short, mealy. 



Weak 

Crumbly, mealy... 



Acid cut. 

Straight. 
Acid cut. 
Straight. 
Acid cut. 

Straight. 

Acid cut, slightly. 

Straight. 

Acid cut. 

Straight. 
Acid cut. 

Slightly faded. 
Acid cut. 



Straight. 
.\cid cut. 
Straight. 



Average score on flavor of cheese made with normal acid, 39. 
.\verage score on flavor of cheese made with high acid, 35.5. 

As will be noted from Table 6, the milk was not perfect at any time 
during which the experimental cheese was made, neither was it very 
bad, and there was no difficulty in making a cheese that commanded 
full market price. There was a slight taint, also a few pin holes that 
worked out easily in the matted curd. It was perhaps unfortunate 
in some respects that the milk was not perfect for a few of the lots. 



16 



INFLUENCE OF LACTIC ACID ON QUALITY OF CHEESE. 



But the results of the experiment are so positive that it can not be 
consitlered otherwise than conchisive. 

A study of the numerical and descriptive scores in Table 6 shows 
that high acid has a markedly injurious influence on the flavor. 
The bad flavors in the cheese made up sweet were in ever}' case less 
pronounced than in that of the same lot which was made up acid. 
In addition other bad flavors appeared in the acid cheese that were 
not apparent in the cheese made normallv. The sweet or fruity flavor 
that was noticed in all the cheese was more pronounced in the high 
acid than in the normal cheese of the same day. In five out of the 
eight lots a bitter flavor in the acid cheese appeared that was not 
noticeable in the normal cheese of the same day. A sour or old 
whey flavor appeared in most of the high-acid cheese. 





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Fig. 2.— Diagram showing relation of acidity to score of liigli-acid and normal cheese. 
RESULTS OF EXPERIMENTS CONTRARY TO GENERAL PRACTICE. 

These results are certainly very radical in view of the belief of 
cheese makers and the teaching of experts to the contraiy. The 
great majority of cheese makers believe that a high development of 
acid is an antidotie for bad flavors of all kinds, and that it is about 
the only means they have of fighting bad flavors as well as gas. 
Whenever a period of bad milk comes and the product is off flavored 
or gassy, the effort has always been made to develop a maximum of 
acid in the whey as a preventive of the trouble. It has, in fact, 
usually been considered advisable, where the trouble has been pro- 
nounced, to make a slightly high-acid cheese, as the high acid has 
been considered the less of the tw^o evils. This practice is taught by 
dairy instructors and recommended by many cheese dealers who act 
as advisers to the cheese makers from whom they buy. The result 
has usually been that after a few lots of })()or cheese were made at a 
factory a period of high-acid cheese followed. The foregoing experi- 



EESULTS OF TESTS WITH HIGH-ACID CHEESE. 17 

ments prove that this tendency to develop excessive acid is poor 
poHcy. In fact, instead of minimizing the faults it makes them more 
pronounced, as well as adding new faults to the product. 

It is universally believed and taught that a maximum development 
of acid in the whey is necessary for a satisfactory and maximum 
development of acid in the matted curd. Dean,'^ in some of his work, 
seemed to show that the curd was ready for grinding and for the press 
at the same time regardless of the percentage of acidity at which the 
milk was set or the whey drawn, vats of divided milk being used for 
the experiments. In view of the fact that the bacteria are held 
within the curd particles and the acid is consequently developed in 
the curd, we have no reason to believe that this development would 
not go on as fast in the matted curd as in the whey. This would 
appear to be much more reasonable than the old idea that a maxi- 
mum development of acid in the whey was necessary to hurry the 
process. 

While a high acidity is needed to exclude undesirable forms of 
bacteria and give the cheese its desired characteristics, this high 
acidity can develop in the matted curd. That there is no virtue in 
a high development of acid in the whey can be seen from Table 5. 
The taint and the gas were as bad in the curd allowed to remain in 
the whey until a high acid was developed as they were in the curds 
from the comparatively sweet whey. The development of high acid 
in the whey did not have any effect on the growth of injurious bac- 
teria, as far as could be judged from the product. The maximum 
amount of acid in the whey at time of drawing is about 0.2 per cent, 
and this is generally considered to be insufficient to check most of 
the injurious bacteria. It is the comparatively high-acid develop- 
ment which takes place in the matted curd that holds these bacteria 
in check. 

From all this evidence there is but one conclusion to be drawn, 
namely, that the teaching which led to a maximum development of 
acid in the whey was wrong. The high acid developed in the whey 
is likely to cause much injury, and from the evidence at hand it does 
no good. With our present knowledge, however, it can hardly be 
advised to go to the other extreme and run the whey as sweet as pos- 
sible, but it is certamly evident that the whey should be run suffi- 
ciently sweet to leave no possibility of making a high-acid cheese. 

An interesting feature of the results of the experiments shown in 
Tables 1 and 2 is seen in the lots where only part of the cheese turned 
out to be high acid. The cheeses in those lots that were placed in 
storage direct from the press showed no evidence of high acid, while 
those that remained in the factory curing room for a time before going 

o Twenty-second Annual Report, Ontario Agricultural College, 1896, p. 54. 



18 INFLUENCE OF LACTIC ACID ON QUALITY OF CHEESE. 

into storage were injured in texture and color. The point in this 
connection lies in the fact that the cheese that was injured in texture 
and color was likewise injured in flavor. Whether the low score on 
flavor was simply coincident with the low score on texture and 
color and due to the longer time that the cheese was held out of stor- 
age, or whether there is some vmexplained connection between the 
injury in texture and the injury to flavor, might seem open to question. 
It would appear that the former was the case in part. If the latter 
be true it must be considered that the point in acidity which injures 
the texture also injures the flavor. There are reasons to believe that 
this is true, or at least that the point of acidity at which the flavor 
is injured and the point at which the texture is injured are not very 
far apart. 

There is therefore a question in connection with this which may 
be investigated with profit. Whey can be drawn with 0.2 per cent of 
acid without injury to the texture of the curd. Any acid above this 
evidently injures both texture and flavor. Does the injury to tex- 
ture and to flavor begin at the same point in acidity, or does injury 
to flavor begin with a lower acidity than 0.2 per cent ? 

THE USE OF STARTER IN MILK. 

Nothing in this discussion should be interpreted as being opposed 
to the use of a good starter in the milk before setting. The develop- 
ment of acid is, according to our present knowledge on the subject, 
necessary to overcome the growth of gas-producing and other unde- 
sirable forms of bacteria. Bacteriological investigations have shown 
that if there is a sufficient number of lactic-acid bacteria as compared 
with the other kinds, the lactic-acid bacteria increase to the partial 
exclusion of many other kinds. When the lactic acid has developed 
to a relatively higli degree it makes the milk or the curd an unfavor- 
able place for many kinds of bacteria to grow. The starter can be 
added usually without any danger of increasing the acidity to a 
point where it will be difficult to cook to a proper degree of firmness 
before too high acidity has developed in tlie whey. 

EFFECT OF EARLY STORAGE ON ACID CHEESE. 

This work may be considered a continuation of previous work 
carried on by the Dairy Division at Plymouth during the summer of 
1905." It was planned to determine definitely some of the results 
which showed incidentally in the previous work. The main point 
which it was desired to cover was the effect of low storage tempera- 
tures on high-acid cheese. 



o Bureau of Animal Industry Bulletin 85. 



EFFECTS OF EARLY STORAGE ON ACID CHEESE. 19 

In the report on the previous storage work at Plymouth atten- 
tion was called to the fact that in two or three lots of cheese used 
in the tests the cheese which was left in the factory curing room for 
from one to two weeks at a temperature of from 55° to 70° F. showed 
decidedly too much acid, almost a so-called ''dead sour" in one case. 
The ones from the same lots (including the dead-sour lot) which 
went directly from the hoop into the rooms held at 32° and 40° F. 
were very slightly acid, in fact showed so little evidence of too much 
acid that the selling price was not affected in the least. This was a 
decidedly interesting point, and as practically all cheese dealers held 
entirely opposite views, a thorough demonstration of the results 
obtained would be of economic importance as well as of scientific 
value. 

At the present time most of the cheese dealers protest against 
receiving a cheese under one week of age, because in a young cheese 
too much acid can not be readily detected. If it can be satisfactorily 
shown that a cheese which does not show too much acid at the time 
it goes into storage will come out of storage in good condition the 
objection on the part of the dealers to receiving very fresh goods 
would be entirely overcome, so far as high acid is concerned. 

A reference to Tables 2 and 3, which give details of experiments 
intended to cover this point, shows that the sooner a high-acid 
cheese is placed in cold storage the better it is for the cheese. This 
is borne out by the scoring of the cheese in lot 1. The cheese that 
was left in the factory curing room for a week before going into 
storage showed decidedly acid and was badly injured, while that 
which went directly into storage was not injured in either texture 
or color. In all the other lots the scores show that the effect of the 
high acid was minimized by early storage. 

The favorable effect that immediate storage has on high-acid cheese 
was very clearly demonstrated also in Table 1. Lots 4, 12, 14, 15, 
16, 19, 20, 22, 26, and 31 described in this table were evidently 
made up with too much acid. The portions of these lots that 
remained in the factory curing rooms for aiiy length of time after 
making showed defects in texture and color, while those that went 
directly into storage were not injured in the least. The average 
score on the high-acid lots of the cheese just referred to that went 
into storage at once was 78, while the average score of the lots that 
went into storage in one week was 74. Similarly the scores of the 
lots in Table 2 were 72.5 and 67.2, respectively. 

In so-called dead-sour cheese early storage will minimize the 
damage, but it is not a cure, as is evidenced by lot 5 in Table 3. How- 
ever, the buyers can usually detect these very sour cheeses at an early 
age, and there is no danger of deception. From these experiments 



20 INFLUENCE OF LACTIC ACID ON QUALITY OF CHEESE. 

it would appear that the objection on the part of the buyers to 
handhng a cheese direct from the press is not well founded. 

CONCLUSIONS. 

1. In the process of making Clieddar cheese a too high develop- 
ment of whey acid injures the flavor as well as the. texture of the 
curd. 

2. The development of acid in the matted curd overcomes gas 
and bad taints and does not injure the flavor and texture. 

3. Cheese with high acid should be. put into cold storage as early 
as possible to minimize the bad effect of the acid. 



o 



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LIBRARY OF CONGRESS 



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